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    <script>
      // 多维数组
      const arr = [[1, [2]], 3, [4, [5, [6, [7]]]]];
      // 数组的扁平化（将多维数组变成1维数组）
      // arr.toString().split(',').map(Number)
      console.log(arr.flat(Infinity));
    </script>
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